Fix caching bug in JPEGImageDecoder

Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp

Index: Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
diff --git a/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp b/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
index 59ae3c81f2557edeef572f0a271593353c66cf7b..8f9eae71b94eae5cf7150bb97a685cb38b3b93f7 100644
--- a/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
+++ b/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
@@ -240,4 +240,35 @@ TEST(JPEGImageDecoderTest, byteByByte)
     testByteByByteDecode(&createDecoder, "/LayoutTests/fast/images/resources/red-at-12-oclock-with-color-profile.jpg", 1u, cAnimationNone);
 }
 
+static unsigned createDecodingBaseline(SharedBuffer* data)
+{
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(data, true);
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    return hashBitmap(frame->bitmap());
+}
+
+TEST(JPEGImageDecoderTest, mergeBuffer)
+{
+    const char* jpegFile = "/LayoutTests/fast/images/resources/lenna.jpg"; // 256x256
+    RefPtr<SharedBuffer> data = readFile(jpegFile);
+    ASSERT_TRUE(data);
+
+    const unsigned hash = createDecodingBaseline(data.get());
+
+    RefPtr<SharedBuffer> segmentedData = SharedBuffer::create();
+    segmentedData->append(data->data(), data->size());

[Peter Kasting, 2015/09/19 00:51:34]

You should have comments in this test about what you're actually doing and why
it works.

[scroggo_chromium, 2015/09/21 18:21:28]

Done.

+
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(segmentedData.get(), true);
+
+    ASSERT_TRUE(decoder->isSizeAvailable());
+
+    segmentedData->data();
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    ASSERT_FALSE(decoder->failed());
+    EXPECT_EQ(frame->status(), ImageFrame::FrameComplete);
+    EXPECT_EQ(hashBitmap(frame->bitmap()), hash);
+}
+
 } // namespace blink